典型黑土耕地土壤优先流环绕特征

Surrounding characteristics of preferential flow in cultivated typical black soils of Northeast China

以典型黑土耕地土壤为研究对象,采用双环入渗仪和染色示踪技术相结合的方法,通过对图片的判读,测定与分析了染色宽度、横纵剖面染色百分比和田间最大染色深度,以研究典型黑土耕地土壤的水分运移形式及其分布特征.结果表明:在0～15cm土层范围内,水分的运移以基质流为主;15～20cm范围内,有侧向入渗发生,平均染色宽度和染色百分比均在此层达到最大值,分别为23cm和20.73%;20～67cm范围内,水分的运移则以大孔隙流为主,优先路径主要是裂缝和大孔隙,其中,20～35cm范围内的大量裂缝使优先流表现出明显的环绕特征;而在40～67cm范围内,优先路径的形成则以连通性良好的大孔隙为主.由于裂缝和大孔隙2种优先路径的存在,使水分在土壤中的运移速度增加了4.5倍,这不仅可能造成水分损失,而且可能加速农药迁移造成地下水污染.建议在黑土区土壤的耕作和经营过程中,应当减少和消除这些优先路径.

Taking the cultivated soils in typical black soil region of Northeast China as test objects, and by using dye tracer and double-ring infiltrometer techniques and photograph interpretation method,this paper measured and analyzed the dye-stained width and dye-stained coverage of soil transverse and longitudinal sections as well as the field maximum dye-stained depth,aimed to approach the water flow movement pattern and distribution characteristics in test soils. At soil depth 0-15 cm,matrix flow was the main soil water flow movement pattern; at depth 15-20 cm,lateral flow was observed,and the average dye-stained width and dye-stained coverage reached their maximum, being 23 cm and 20. 73 % ,respectively. At depth 20-67 cm,the main soil water flow movement pattern was macro-pore flow,with cracks and macro-pores as the main preferential routes. The cracks at depth 20-35 cm made the preferential flow have distinct surrounding characteristics,and the macro-pores at depth 40 - 67 cm were the main preferential routes. Due to the existence of the preferential routes of cracks and macro-pores,the migration velocity of water in soil increased by 4. 5 times,which could not only cause water loss,but also accelerate the migration of pesticides to ground water. It was suggested that these preferential routes should be decreased or eliminated during the cultivation and management on cultivated typical black soils.